Sail repair – how to extend the life of your mainsail – Practical Boat Owner Magazine

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Rupert Holmes explains how maintenance and timely sail repair can maximise the life of your sails.
After 24,000 miles – including three visits to the Azores, racing round Britain and Ireland and a foray into the Atlantic – it was a simple day-race (round the Isle of Wight) that finally killed Zest’s last mainsail.
Sails are often the most expensive things we will buy for the boat, even outstripping electronics, so it’s hardly surprising that most of us try to maximise their life.
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The problem with Dacron – stretch…
Dacron is by far the most popular material for cruisers as it’s relatively cheap (by sailmaking standards), retains strength for a long time and is easily repairable. Unfortunately, it’s also a stretchy material, a factor that becomes more pronounced as the sail ages.
It’s often said this stretch doesn’t really matter much for cruising. That might be true if all your sailing is running downwind in the tropics, but few of us are that lucky. The problem with a misshapen sail goes far beyond the loss of a little speed – it also adds to the boat’s heel and increases weather helm. The boat is therefore more difficult to steer, whether by a crewmember or an autopilot, and the motion at sea becomes more uncomfortable.

7 quick tips
1 Never let the sail flap any more than is absolutely necessary. This can’t be emphasised enough.
2 Keep checking sails over for problems and pre-empt damage wherever possible. Reinforcing a weak area is quick and inexpensive, but when a tear starts it can propagate very quickly, leading to a big repair job.
3 Schedule a mid-life refit, adding a two-ply leech and reinforcing any other areas of weakness.
4 Fully battened sails last better and will tend to retain their designed shape for longer than those with conventional short battens.
5 Pay close attention to chafe protection on spreaders and shrouds.
6 Tension the leech line toprevent the leech of the mainsail from fluttering.
7 With care even high-tech sails have potential to last as long as some Dacron materials and will retain their designed shape almost throughout their life.
High tech laminate and membrane sails, as well as the latest generation that rely on advanced resins instead of plastic film, all solve the problem of stretch. However, historically they suffered from a reputation as having a short lifespan. This was well deserved for early sails made of Kevlar that were the preserve of the racing scene.
Technology has moved on enormously however – it’s been well over 20 years since this type of sail first gained popularity on performance cruising yachts and they’ve been well proven in that time.
Much of the longevity of Zest’s mainsail was down to it having been carefully looked after. This is particularly important for a high-tech sail, especially those that use a Mylar film. With these sails, what might initially appear to be a small area of damage can propagate very quickly, with the potential to render the sail beyond sensible repair.
When my partner, Kass Schmitt, bought Zest (a 36ft custom design by Rob Humphreys) in 2013, the top-spec membrane mainsail – built by Elvstrøm in 2007 for ocean racing – had hardly been used and was like new.
It was retrofitted with a third reef by OneSails in Hamble, but other than that, and regular visual checks for signs of damage, we paid little attention to the sail aside from ‘sticking plaster’ repairs using thin self-adhesive Dacron on any areas of chafe on the protective taffeta outer layers.
Mid-life failure
Repairing a reinforcement patch.
At 12,000 miles we had the first – and only – mid-life failure, when the fibres below the third reef gave out when gybing in 30 knots of breeze, resulting in a 6in tear. We got a heavy-duty multilayer repair that bridged the reinforcement between the second and third reef points. At the same time the sailmaker recommended adding a second layer of fabric to the leech above the third reef. Given this is the most loaded part of a sail, and also flogs the most when the sail is flapping, such a two-ply leech can all but eliminate failure in this part of the sail at a later stage.

At the same time he also added reinforcement around the ends of the batten pockets. Without doubt this attention mid-life was key to the sail’s longevity and reliability at a minimal cost compared to a new sail of similar quality.
After this it covered four passages of more than 1,000 miles, plus two Fastnet races and numerous shorter trips along the South Coast and across the Channel.
Before 2019’s AZAB (Azores and Back Race) we took the sail, which had by then covered more than 20,000 miles, back to Paul. He added more material in way of the reinforcing patches of the lower two reefs, where hinging of the cloth as it steps down in thickness had weakened the fabric due to flex damage. He also attended to some flex damage at the inner edge of the two-ply leech that had been fitted 8,000 miles earlier and replaced the leech tabling.

Easy sail repair tips
Until a few years ago repairing a mainsail meant either painstaking handstitching, or the hassle and time of removing the sail from the boat and taking it to a sewing machine. That has changed with modern adhesives such as Dr Sails. This is a super-strong flexible two-part epoxy resin that cures to 80% of its final strength in just 20 minutes. It’s also easy to apply thanks to a nozzle in which the two parts are automatically mixed. This means small, and in some cases even medium sized, sail repairs can be carried out in-situ and in only a few minutes. I’ve successfully used it on structural repairs that have lasted thousands of miles. The only downsides are the adhesive is a slightly yellow colour and it’s relatively expensive in small tubes. That said, a 265ml cartridge costs less than £50 and additional nozzles are sensibly priced. With a three year shelf life, and given that the same cartridge can be re-used multiple times with new nozzles, it’s well worth carrying on board.
The eventual demise
The sail’s eventual downfall was associated with an excess of flogging. Part of the problem was an unusual challenge in 2019’s Solo Offshore Racing Club’s RIOW (Round Isle of Wight) race. We started from Cowes, heading west towards the Needles against the tide. That meant repeatedly short tacking in the weaker stream close to the shore, repeatedly crossing tacks with the 21 other competitors. My track showed 29 tacks over a straight line distance of only 13 miles.
The early stages were in light airs, but the wind increased in the Needles Channel, with true wind speed in the gusts topping 20 knots. Although Zest is well set up to reef quickly, to do so still risked popping out into deep water and quickly losing places in the strong adverse tide. I therefore held on, playing the mainsheet and traveller to depower in the puffs.
Nevertheless, it wasn’t long before every tack saw more taffeta and Mylar film detaching from the sail, accompanied by increasing depth in the middle of the sail as the structural fibres started to slip past each other.
Fortunately, it was still useable after turning downwind at the Needles and I was able to nurse it around the rest of the course, in the knowledge that its replacement was already on order (and we had an older, though little used, Dacron spare that could be pressed into service if necessary).
Could you add battens?
Zest’s new main is fully battened which will extend its life.
An old adage of seamanship is that ‘a stitch in time saves nine’. That’s just as true today as it was 300 years ago, but regularly checking for damage and making repairs is not enough on its own to maximise a sail’s life.
How well the sail is treated is also a factor. It’s easy to think that flaking it carefully on the boom is the most important element of taking care of a sail. While that’s clearly helpful it’s only a relatively small part of the story – what you do with the sail when it’s hoisted is far more important.
The big problem is flapping and flogging, which rapidly breaks down the structure of all sail fabrics. The more you can minimise this the longer your sails will last and the lower the risk of unexpected damage. This explains why, whatever material the sail is made from, fully battened sails will always last longer than conventional ones built of the same cloth.
While usually the choice to opt for a fully battened sail has to be made when the sail is new, it may be possible to economically retrofit full battens to an existing sail. The barriers to making this cost-effective tend to be in the cost of the batten material and luff cars, rather than the simple task of sewing in longer batten pockets.
Nevertheless, I successfully retrofitted full battens to the mainsail of Ammos, my Discovery 3000 in Greece, which has noticeably reduced the rate of degradation of the cloth. I was fortunate in having been able to rescue second-hand battens that could be cut down to size from a sail that had been discarded at the end of its life.
Efficient reefing systems
Efficient reefing systems also reduce flogging, simply because they speed up the process of either tucking a reef in, or shaking one out. Good racing crews even back up in reverse gear when hoisting or lowering the mainsail to reduce the apparent wind strength. This means the sail flaps more gently and therefore results in less wear and tear on every outing.
Motor sailing is the situation in which cruising yachts are most likely to have the whole mainsail flapping for an extended period. The solution is to strap the sheet in as hard as possible and point a few degrees off the wind to keep wind in the sail. If I’m expecting to be motoring in a calm for an extended period I’ll drop the sail and stow it to prevent accelerated wear, even if that means hoisting it again when a favourable breeze returns.

Leech lines

The leech of any sail has a tendency to flutter, which can degrade the cloth very quickly. Tensioning the leech line prevents this, but with many mainsails it’s not always easy to adjust as leech line cleats are positioned on the back of the sail and therefore out of reach near the end of the boom. On a quality sail the leech line should start at the clew, run through a pulley at the head of the sail and then be led down to cleats on the luff of a sail at each reef point, where it’s easy to reach for adjustment.
Chafe protection

It’s also important to pay attention to chafe protection on spreaders and shrouds. Self adhesive spreader patches with thick padding can be excellent, but batten pockets may also need webbing glued in place to protect against chafe on the shrouds. This is particularly the case with some high tech sails, where the batten pocket itself carries the sail’s structural fibres.

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